Cystocoleus ebeneus  (Dillwyn) Thwaites

   Thallus filamentous, forming wefts or mats, made of black filaments placed in small tufts, without order nor orientation; microscospic observations at low enlargement ratio show surfaces with knobbled filaments, sometimes branched at right angles with small spiky branches; at high magnification ratio, filaments corrrespond to mycelium hyphae, dark-brown, tortuous, branched, forming a dense network closely surrounding and adhering to single filaments of the photobiont (Trentepohlia), without delimiting rectangular spaces. Rare, on more or less vertical siliceous rocks of exposed and windy ridges but avoiding direct wetting, often in combination with other lichens of these habitats (Lepraria) and Trentepohlia or free Cyanobacteria. Quite easily confused with Racodium rupestre much  more common and growing everywhere on humid rocks. A microscopic observation is often required for identification. The latter displays hyphae organised in parallel delimiting rectangular spaces.*